Epidemiologic studies have correlated dietary intake data with the incidence and mortality from prostate cancer. Dietary fat is one nutritional variable which often shows a strong positive correlation. An objective of this proposal is to study the effect of dietary fat level on the growth of transplantable prostate tumors in rats. Since the prostate, like the mammary gland, is regulated by the endocrine system it is reasonable to hypothesize that dietary effects on prostate function or tumor growth may be mediated by hormonal changes. A second objective of this grant is to evaluate the interactions of dietary tumor growth. Two experiments are described in this proposal. The first will determine the effects of graded levels of dietary fat on the growth of the Dunning hormone dependent (R-3327-H) and hormone independent (R-3327-HI) trnsplantable prostate adenocarcinomas. Diets varying in fat level, 0.6% linoleic acid, 5% corn oil, 10% corn oil, and 20% corn oil) will be fed. Protein, minerals, vitamins and fiber will be supplied at a constant ratio per kilocalorie of dietary energy. The effect of diet on tumor size, composition and hormone receptor binding (testosterone and prolactin) will be determined. Serum prolactin, FSH, LH, growth hormone, FSH, and LH will also be determined. The second study will determine the effects of elevated or reduced plasma prolactin on the growth of the R-3327-H and R-3327-HI tumor lines. Serum prolactin will be elevated in one group of rats by multiple dosing with ergocryptine (CP-154). In a second group, serum prolactin will be elevated by pituitary transplants under the kidney capsule. A third group of rats will have no hormonal manipulation. The effect of prolactin on tumor growth, composition, hormone receptors and serum hormones will be determined.